RFID tags are known in the art. These so-called tags often assume the form factor of a label or a literal “tag” but are also sometimes integrated with a host article and/or its packaging. RFID tags typically comprise an integrated circuit and one or more antennas. The integrated circuit typically carries out a variety of functions including modulating and demodulating radio frequency signals, data storage, and data processing. Some integrated circuits are active or self-powered (in whole or in part) while others are passive, being completely dependent upon an external power source (such as an RFID tag reader) to support their occasional functionality.
There are proposals to utilize RFID tags to individually identify individual items. The Electronic Product Code (EPC) as managed by EPCGlobal, Inc. represents one such effort in these regards. EPC-based RFID tags each have a unique serial number to thereby uniquely identify each tag and, by association, each item associated on a one-for-one basis with such tags. (The corresponding document entitled EPC Radio-Frequency Identity Protocols Class-1 Generation-2 UHF RFID Protocol for Communications at 860 MHz-960 MHz Version 1.0.9 is hereby fully incorporated herein by this reference.)
Each EPC-compliant tag has two states for each supported session: “A” and “B.” The “A” state comprises the default state and hence represents the tag's state when initially powering up. Once a tag has been read by an RFID-tag reader its state changes from “A” to “B.” During the “A” state a tag will respond to any reader that offers a session query. During the “B” state, however, the tag will not again respond to a reader using the same session query. EPC's four different sessions provide for differences with respect to how a read tag persists a “B” state upon losing power.
Pursuant to one approach to system design, RFID-tag reader energy is highly dispersed through a given monitored facility. Examples in such regards can be found, for example, in U.S. patent application Ser. No. 12/900,191, entitled METHOD AND APPARATUS PERTAINING TO RFID TAG READER ANTENNA ARRAY (the contents of which are fully incorporated herein by this reference). Notwithstanding the various benefits afforded by such an approach, in many cases a given RFID tag within such a facility may only be read occasionally as the RFID tag, once read, may persist its “B” state due to the generally-ubiquitous section-wide availability of power. This means, for example, that a tagged item might be read once initially upon first entering the sales floor of a retail facility but will then move quietly (in its “B” state) through the sales floor to a final destination such as a display of loose inventory.
Accordingly, the RFID-tag system may be able to confirm that this particular item entered the sales floor, but will not be able to otherwise account for a present location of that item. Difficulties in these regards are made worse by the fact that many retailers often display identical products in a variety of different locations within their facility. For example, a given item might be stocked as loose inventory on a shelf in a first part of the facility while other identical items are displayed in a so-called end-cap display elsewhere in the same facility. As a result, even knowing via an RFID-tag monitoring system that a particular such item did indeed enter the sales floor, the system will be uncertain as to the actual location of that item within the facility absent more aggressive inventorying methodologies.
Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. Certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.